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How can coal-derived synthesis gas be used to make liquid fuels?
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coal utilization
Cross-regenerative coke oven. (A) Cross section, showing the alternating arrangement of flue walls and ovens; (B) longitudinal section, showing (left) a series of combustion flues in a single flue wall and (right) part of a long, slotlike oven.
Coal-derived synthesis gas (syngas) is converted into liquid fuels primarily through a process known as indirect liquefaction, most notably the Fischer-Tropsch (FT) reaction.12
The production process generally involves two main stages:
- Gasification: Coal is first converted into syngas—a mixture consisting primarily of hydrogen and carbon monoxide—by reacting it with steam and oxygen at high temperatures and pressures.312
- Synthesis: The resulting syngas is then passed over a catalyst, such as iron or cobalt, at elevated temperatures and pressures. This triggers the Fischer-Tropsch reaction, which chemically recombines the hydrogen and carbon monoxide into a wide range of liquid hydrocarbons, such as gasoline and diesel fuel.314
Because coal is hydrogen-deficient compared to liquid fuels, this indirect method effectively builds the desired hydrocarbon chains from the gaseous components derived from the coal structure. This technology has been utilized historically for fuel production and remains a significant source of liquid fuels in regions like South Africa.21